Do you have an idea if it's rats or mice? If it's mice, you can use mouse traps, I get mice in my house (basement) and I've had good success with peanut butter and Victor's quick set traps
Because i think you would be safe for otters but not sure about birds...
If you do use the rat poison, maybe try to put it where you found the nest, hopefully out of access from anything else, like dogs or cats too...
Jay